Previously, many types of mechanisms have been used to provide an effective means of maintaining a parallel relationship of at least one pair of fiat platforms while permitting expansion or contraction of movement in a straight line or in a Z-axis linear direction. Most prior art has utilized arms, jointed at the ends, in concert to achieve this motion. The field of robotic manipulators has been replete with this type of device, however in most cases little consideration has been given to maintain a precise relationship or parallelization on an accurate linear and tilt-free translation useful to precision equipment.
A search of the prior art did not disclose any patents that read directly on the claims of the instant invention, however the following U.S. patents are considered related:
Patent No. Inventor Issue Date 5,721,616 Domenicali Feb. 24, 1998 5,237,887 Appleberry Aug. 24, 1993 5,156,062 Appleberry Oct. 20, 1992 4,976,582 Clavel Dec. 11, 1990 4,806,068 Kohli et al. Feb. 21, 1989 4,651,589 Lambert Mar. 24, 1987 4,248,103 Halsall Feb. 3, 1981 2,569,354 Tracy Sep. 25, 1951 2,506,151 Hoven et al. May 2, 1950 2,338,533 Pash Jan. 4, 1942 2,198,635 Rossman Apr. 30, 1938
Domenicali in U.S. Pat. No. 5,721,616 teaches a tilt-free linear micromotion translator such as an optical element, which includes a flexural suspension connected to a workpiece along a predetermined transitional axis. The flexural suspension utilizes a number of flexural links connecting points on a fixed rigid frame member. The links lie in a pair of parallel planes with the transitional axis normal to the paralleled planes. The device includes a linear motion transducer to the suspension, enabling tilt-free linear micromotion.
U.S. Pat. No. 5,237,887 issued to Appleberry discloses an apparatus which includes a static base, a platform, a first arm assembly, and a second arm assembly. The first arm assembly has a first terminal portion pivotally connected at a first pivot point to a first portion of the static base and a second terminal portion pivotally connected to the platform at a second pivot point. The first arm assembly is constructed to permit changes in the distance between the first and second pivot points, but is concomitantly constrained to movement in a desired first plane. The second arm assembly has a respective first terminal portion pivotally connected at a third pivot point to a second portion of the static base and a respective second terminal portion pivotally connected to the platform at a fourth pivot pointy. The second arm permits changes in the distance between the third and fourth pivot points but is constrained to movement in a desired second plane which is angularly disposed from the first plane. The motion of the platform is constrained to a straight line when the distance between the first and second pivot points and/or the distance between the third and fourth pivot points is changed.
U.S. Pat. No. 5,156,062 issued to Appleberry discloses an apparatus for maintaining the angular position of a platform during motion of the platform in any direction relative to a base. The apparatus includes a static base, a platform, a first arm assembly, a second arm assembly and a third arm assembly. Each arm assembly has one terminal portion connected to a portion of the static base, by a first universal joint and another terminal portion, connected to the platform, by a second universal joint. Each arm assembly is constructed to permit changes in the distance between its universal joints, but concomitantly removes a degree of angular freedom from the platform. The angular position of the platform is thereby maintained when the distance between the respective universal joints is changed.
U.S. Pat. No. 4,976,582 issued to Clavel includes a base element and a movable element along with three arms mounted with three shafts attached with linking bars forming connecting assemblies. The inclination and orientation of the moveable element remains unchanged regardless of the motion of the three control arm assemblies. The movable element supports a working element of which the rotation is controlled by a fixed motor situated on the base element.
U.S. Pat. No. 4,806,068 of Kohli et al. discloses a robotic manipulator for supporting a workpiece. The manipulator has a rotary linear actuator mounted on a base providing controlled movement of a link with two degrees of freedom. The link has one end spherically joined to a movable member which supports a workpiece. The link is articulated with the opposite end supported by a linear actuator.
Lambert in U.S. Pat. No. 4,651,589 teaches a polyarticulated mechanism having three legs situated in separated planes and formed in two parts, each associated on a spherical end and the other end to an endmost piece.
U.S. Pat. No. 4,248,103 issued to Halsall is for linkage mechanisms for industrial manipulators of the straight line conchoid type. The linkage mechanisms move in straight lines without the use of lead screws of revolute jointed arms.
For background purposes and as indicative of the art to which the invention is related reference may be made to the remaining cited patents issued to Tracy, Hoven et al., Pash and Rossman.